make sure all the parts are grouped and you select the group and freeze transform. If you drag select multiple objects then try to translate them they all move based on their own transform nodes.
Also be sure that you clear history. If you perform nurbs operations like booleans, trims, cuts, fillets, etc and try to move the objects while they still have history they will go all wonky as well.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675